Automatic charging of electric furnaces



Dec. 9, 1930. P. L. J. MIGUET AUTOMATIC CHARGING OF ELECTRIC FURNACES Filed March 20, 1929 Patented Dec. 9 1 930 i UNITED STATES PATENT OFFICE AUTOMATIC CHARGING OF ELIIEICZIRIG FURNACES 7 Application filed March 20, 1929, Serial No. 348,646, and in France December 6, 1928.

This invention relates to improvements in. means for automatically charging electric furnaces.

In my concurrent U. S. application for electric furnaces, Serial No. 348,645, filed March 20, 1929, I have described improvements in the supplying of current which eliminates almost completely the use of sandwiched conductors and allows for closing the 18 furnace for gaseous recuperation under particularly favourable conditions as to simplicity and security.

It has been shown also that the closing thus permitted permits the use of any current intensity up to'500,000 amperes and over because of the possibility. of obtaining regulation of the power by varying the applied voltage instead of by varying the height of the electrode, the airtight current supplying 20 band requiring a semistationary electrode that is to say an electrode subjected only to periodical lowerings to compensate for use.

Although this method of control would not be suitable for large voltage differenceswhich necessitate the use of homogeneous fusion beds, it is very applicable on the other hand for the heterogeneous fusion beds described in French Patent No. 606428 dated November 4; 1925 for stabilizing the chemical resistance of furnaces laterally fed with current into the mass of material, care having to be continually taken for introducing into the feed hopper additional corrective material to limit the leakage of gas and keep it full of conducting material.

Further, to make the additions opportunely it is necessary, whatever the state of reduction immediately following each casting or in each period of time between charges to introduce these additions at the base of the feed hopper itself, that is to say into the part of the hopper most unfavourable for feed mechanism since it is under the most direct influence of the furnace. In practice it is impossible to provide mechanism as strong and airtight as it should be to meet said conditions, this fact leading to the rejection of a process of reduction the advantages of which are recognized in open furnaces.

According to the present invention, the

first materials are so fed individually into the fusion beds that in the furnace the mass being treated is divided into groups arranged in succession in sections dissimilar in content although juxtaposed like the segments of an orange. In this way there may be side by side for carbide of calcium first a section of carbonaceous material and a section of lime, secondly a further section of carbonaceous material and a further section of lime, or for 76% 80% manganese first a section of carbonaceous material and two sections of pyrolusite and a section of carbonaceous material and a section of lime, secondly a further section of'carbonaceous material and two further sections .of pyrolusite and afurther section of carbonaceous material and a further section of lime.

For the laterally continuous heterogeneous fusion bed of known processes,the conductivity of which is lessened by the content of material to'be reduced and the necessary additions to the charge, the present process substitutes a laterally discontinuous bed containing sections of carbonaceous material, the conductivity of which is constant because none of the material to be reduced is mixed therewith. Instead of a general flow of current through a heterogeneous mixture of varying cnductivity there is a localized current flow'of greater constancy and efliciency.

In fact the localized flow thus produced gives both greater efficiency' and greater stability, than general flow obtained with a conducting mixture in the heterogeneous fusion beds, which togethpr with the possibility of dispensing, by interposition of carbon sections, with all points of contact between sections of contrary natures, allows this new process not only to stand up to the particular exigencies of the closed furnace described in concurrent U. S. specification for electric furnaces, mentioned abgve but also to carry out, starting with oxidized materials and more surely with heterogeneous fusion 9 beds, the preparations of all complex alloys as well as all reduction operations and simultaneous refining.

This process affords two advantages, one relating to the carbonaceous material and the other to the material to be reduced. They are of equal importance because they are capable separately or together and according to circumstances of enabling electric furnaces for the treatment of iron to compete with the blast furnace.

Itoperates advantageously because-of its feature of the individual feeding eliminating all mixture and therefore all density classifi-' tion of CO by leading the reduction gas into upper permeable layers of carbonaceous material.

The invention will be described with refer ence to the accompanying drawings:

Fig. 1 is a sectional elevation through the furnace, on the line AA Fig. 2 is a plan, partly in section mid-way up the furnace, through the lines BB and G-C Fig. 3 is a transverse section at 45 of the lower end of a feed hopper, through the line D-D.

The feed shaft comprises a chute 26 ending in tube 25 of reduced diameter. The shaft 26 is also formed with a mid division wall 27 extending almost to the oulet. A rotary eccentrically mounted shaft 28 is mounted transversely of the outlet androtated by a handle 29 through 90 in either direction so as to partially choke the feed of oneor other of the rimary materials 30 or 31.

Feed screw conveyors 32 are arranged horizontally in the upper portion of the feeding device, each individually driven through reduction gearing 33, by compressed air motor 34 which starts up as soon as. any falling off of the primary materials occurs during the operation of the furnace. The

material is supplied from divided hoppers 35 to fill successive sinkings which automatically not only feeds the furnace but also relative to the diameters of the screw and the valved feed tubes keeps it airtight. The airtightness is aided by other means and is almost perfect. A second screw conveyor 36 is arranged in series with the first. An example of the arrangement of the primary materials in the furnace will now be given. On the left (Fig. 2) are shown two sections of carbonaceous material 37 alternately with two sections of lime 38 and on the right are shown two sections of carbonaceous material 37, two

lime 38.

From the foregoing it will be clearly understood that the new process of reduction by individual feeding of the primary mate- -raw material such as coke, hard anthracite,

rock minerals, etc. are unavoidable as in the colonial countries for example.

The invention is not limited to the examples and figures given, for the carbonaceous material may be a mixture of coke and anthracite, anthracite and oil, et cetera and the materials for reduction may contain purify ing materials in insufiicient quantities to warrant a whole section without departing from the invention. The feeding. of the primary materials may be by three or four conveyors side by side with eccentrics, screws, valves et cetera, to correspond, without changing the essential characteristics. a

What I claim as my invention and desire to protect by Letters Patent is:

1. Apparatus for feeding material to a circular electric furnace comprising a plurality of tubes arrange-i around the periphery, a plurality of feed hoppers mounted one above each tube, a screw conveyor at the base of each hopper to convey the material forward to the tube and a second screw conveyor to feed the material into the hopper.

2. Apparatus for feeding material to a circular electric furnace comprising a plurality of tubes arranged around the periphery, a plurality of feedhoppers mounted one above each tube, ascrew conveyor at the base of each hopper to conveythe material forward to the tube, a rotary eccentric at the outlet of each .tube to retard the flow of material, and a second screw conveyor to feed the material into the hopper.

3. -Apparatus for feeding material to a circular electric furnace comprising a plurality of tubes arranged around the periphery, a plurality of feed hoppers mounted one above each tube, a horizontal screw conveyor at the base of each hopper to convey the material forward to the tube, means at the outlet of each tube to retard the flow of material, and a second horizontal screw conveyor to feed the material into the hopper.

4. Apparatus for charging circular electric furnace comprising aplurality of pipes placed about its periphery, a plurality of charging frames mounted each on a pipe, a

sections of pyrolusite 39 and one section of l screw conveyor at the base of each frame for carrying the material to the ipe, an eccentric at the outlet of each pipe or retarding the flow of the material, a second screw conveyor for carrying the material into the frame and a plurality of outlet pipes adapted to collect the gases liberated and through which the charge in the furnace may be agitated.

5. Apparatus for charging electric circula'r furnace comprising a plurality of pipes arranged in pairs and placed about the periphery, a plurality of charged frames mounted at the outlet of each series of twin pipes, conveyor screws arranged in pairs at the base of each frame for carrying the mate rial to each series of twin plpes, an eccentric at the common outlet of each pair of pipes for retarding the flow of one of the materials relatively to the other, other series of pipes arranged in pairs for carrying the material into each frame.

6. Apparatus for charging electric circular furnace, comprising a plurality of pipes arranged in pairs and placed about its periphery, a plurality of charging frames mounted on each series of twin pipes, screw conveyors arranged in pairs at the base of each frame for carrying the material to each series of pair of pipes, an eccentric at the common outlet of each pair of pipes for retarding the flow of one of the materials relatively to the other, another series of screw conveyors arranged in pairs for conducting the material in each frame and for each screw conveyor, a compressed air motor entering in action as soon as there is produced a storing up of the material.

7. A method of charging a plurality of materials to circular electric furnaces which comprises feeding the diiferent materials separately into non-contiguous radial sectors of the furnace.

8. A method of charging a plurality of materials to circular electric furnaces which comprises feeding carbonaceous materials into a plurality of non-contiguous radial sectors o the furnace, and feeding other raw materials into the intermediate sectors.

In witness whereof I aflix my signature.

PAUL LOUIS JOSEPH MIGUET. 

